Title: My Past Experience in
1My Past Experience in Mathematics
Shing-Tung Yau
The Chinese University of Hong Kong Sep. 19, 2003
2- I grew up in the (farming) countryside of Hong
Kong Yuen Long and Shatin. - There was no electricity and no pipe water.
- I took bath in the river when I was very young. I
have eight brothers and sisters and food was
scarce. - When I was five years old, I took an entrance
examination to a good public school. I failed
mathematics because I made the wrong convention - I wrote 57 to be 75,
- 69 to be 96.
3- So I entered a very small village school.
- There were many rough kids from the farm.
- In a matter of half a year, I got serious sick
because of the intimidation of the rough kids and
mistreatment of the teacher. - I rested at home for half a year. I started to
learn how to deal with difficult situation with
classmates and teachers. - By the time when I entered sixth grade, I was a
leader of a small group of students to wander on
the street.
4- My father was a professor. He taught me a lot of
Chinese literature at that time. -
- However, he did not realize that I did not
attend school for a period of time. -
- (Perhaps because I did well at home as I can
recite most of the essays that he asked me to do.)
5- The reason that I did not go to school was that
the teachers did not really teach. I got bored in
school. Then after a while I got bored on the
street, also. -
- There was a joint examination for all primary
schools. I did poorly. However, I was exactly on
the borderline case. -
- The government allowed these borderline kids to
apply for private school and gave them tuition. -
- I got into Pui Ching Middle School.
6- ??
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- ???????,???????,???????,???????,???????,???????
,???????,???????,???????! - ?????
- ????,????????????,???????????,????????????,??????
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7- This is probably one of the best middle school.
-
- Nothing was exciting in the first year of middle
school. I did not do too well that year. -
- However, I learnt much more at home Chinese
literature, Novels (Chinese and Western),
Philosophy, history. All from my father and his
conversations with his students. -
- Although I did not understand Greek Philosophy.
It started to impress me after listening to many
conversation of my father with his students.
8- I started to read the famous Chinese history
books - ?????
-
- I am especially fascinated by ??.
-
- Not only by its beautiful writings, but also by
its original and responsible way to report the
ancient history. -
- Up to present days, I read this book.
-
- The global view of history from a great master
resonants with the thinking of a great scientist.
9- The following essay strikes me
- Though indulged in reading, I do not pursuit
precise meanings. Nonetheless, every time I hit
on something I was so overwhelmed with joy that I
forgot my meals. - ?????
- ???,????,
- ????,??????
-
- I am not bitter for being poor and obscure, nor
am I keen on being rich and famous. - ??????,???????
10- In following years, this has been the guiding
principle of my study of many different subjects. - With my fathers teaching, I started to set the
goal of my life. An important quotation
11 - Zuo's Book of History
- On Immortality
- The first place is to reign benevolently, the
next to gain victory, and the last to say
valuable words. These achievements will stand
for long and not be abandoned. Thereafter they
are called immortal. - ??
- ???????
- ?????,?????,?????,????,??????
- One needs being humble and simple to reach these
goals. A former student of mine recently recited
the following lines from a Tang poem during a TV
interview in China - ????????,?????????
- ??????,??????,????????
- I would rather be at the summit,
- So all mountains will become tiny under me.
- I think he was a bit too arrogant.
12Sima Qian (???) on Confucius (??)
- There are so abundantly many kings and men of
virtue! Widely known by their contemporaries,
their names feel into oblivion soon after they
perished. And yet Confucius, a man in plain
cloth, has been held in great esteem by scholars
of more than ten generations. - ????????,??!
- ????,????,????,
- ????,?????
13- During conversations of my father with students,
many important points of history of philosophy
were mentioned. - Basic principles
- The root of the very existence of matter (basic
axioms, etc) - General phenomena
- Unification of all principles (unified field
theory) - Methods of understanding truth based on logic and
reasoning - How to combine different knowledge and different
phenomena under a general principle - The great philosophers did not simply follow
others in developing their views, not even from
their teachers. They created their own thoughts
(based on previous works.)
14- The goal of writing history of philosophy
- (??) The origin of a philosophical thinking must
come from different sources. It is our goal to
find out such sources. - (??) There are many complicated philosophical
thoughts in the history. It is important to
figure out the treads of their thoughts. - (??) A cortical comments of the occurrence of all
philosophies and their consequences.
15- I also learnt the way to do research with lasting
importance. - Wang Guowei (???)
- The Three Levels To Achieve Breakthrough in
Research (borrowing some lines from Song Ci or
lyric poems from the Sung dynasty) -
- Level One
- ... Last night the west wind withered the
greenery of the trees - In loneliness, I mounted the tall building
- Casting my eyesight along all roads to the edge
of the earth - ??
- ???????,????,??????
16- Level two
- ... For my loosening waist belt I feel no
regret, - For her it is worth being haggard and thin.
- ??
- ???????,????????
- Level Three
- Looking for her a thousand times
- In a crowd
- All of a sudden
- As I turned my head
- There she was
- Standing in the shades of fading lights
- ???
- ???????,????,????,??????
17- In my second year of Pui Ching, I got into a
problem with my teacher. The teacher was a very
devoted head master of my class and clearly meant
well for me. She was shocked to find out that my
father was a professor and poorly paid. -
- Her passion for my future changed my behavior in
classroom. -
- I studied plane geometry in second year of high
school.
18My classmates were not used to reason
abstractly. The mere fact that I listened to my
fathers philo-sophical discussion at home made
me feel at home with axiomatic approach. In
fact, I felt I can understand my fathers
conversation better after I learnt
geometry. The charm to prove elegant theorems
based on simple axioms excites me.
19- With the passion for geometry, I started to
develop my taste for mathematics, which included
algebra. Everything became easy after I found
the subject exciting. -
- I also found the subject of history interesting.
-
- It taught me a global view of everything that I
learnt. - How events happened?
- Why they happened?
- What may happen in the future?
20- At this time, my father just finished writing his
book on history of Western philosophy. His
conversations with students taught me the way
that we should see history in a global manner. -
- This kind of practice deeply influence my way of
looking at my research projects in the later time.
21- Around 400 A.D.
- Liu (who wrote the first book on comparative
literature on Chinese writings up to that period)
???? ?? -
- My body may perish along with time.
- My goal and my ambition will extend with my
theory. - My heart is in resonance with those great men in
ancient days. - My feeling and my theory will go forward for the
next thousand years. - ????,????????????,?????????
22- When I was fourteen, my father passed away. This
was perhaps the greatest shock to my life. For a
long time, I could not believe that my father
left me and the family. -
- The financial situation of the family was really
bad. It was not clear at all that we could still
go to school. The tremendous will of my mother
and the helps of my fathers friends and students
made it possible.
23- This disastrous change of family situation made
me much more mature. The extreme hard-ship
showed difficulty of human relationship, what I
learnt from my father became practical. -
- The poems and the classical essays that I learnt
became much more meaningful. I spent half a year
to read classical literature and history of
China. It became a way for me to relax during
very tense situation in life. The beautiful
poems guided me to appreciate the beauty of
nature.
24- ???????
-
- ????!??????????,??????????????,???,???,???????????
???????????????,?????????????????,?????? -
- ??????!??????????!??????????,?????????????????????
?????,????????????,?????? -
- ?????
25- From Byrons Don Juan II -- A variation edition
by Steffan Pratt - Canto III, 86
- 1. The isles of Greece, the isles of Greece!
- Where burning Sappho loved and sung,
- Where grew the arts of war and peace,
-
- Where Delos rose, and Phoebus sprung!
- Eternal summer gilds then yet,
- But all, except their sun, is set.
- 2. The mountains look on Marathon
- And Marathon looks on the sea
- And musing there an hour alone,
- I dreamd that Greece might still be free
- For standing on the Persians grave, I could
not deem myself a slave.
26- I read a lot of books in mathematics. I thought
about the problems in those books. When I
exhausted all those problems, I started to create
my own problems as I thought that they may be
challenging. - The practice of creating my own problem had been
the most important part of my research in the
future. The textbooks in school did not satisfy
me. I went to library and I went to bookstores
to read books. I spent hours and hours in
bookstore to read books that I could not afford
to buy.
27- When I was fifteen, I started to teach lower
grade level students to earn money. I was proud
that by teaching in a novel way, I was able to
transform some very poor student to become the
best student in class. -
- It was an experience to train young people. I
also learnt that it is beneficial to myself to
teach.
28- My high school teachers in mathematics were
excellent. We studied rather advanced topics in
mathematics. I had no difficulty with them. -
- However, I was rather disappointed that my
physics teacher was not good enough. The
fundamental intuition in physics was not
established during my high school year. I
regretted it up to now. -
- I had an excellent teacher in Chinese. He was my
fathers friend he taught us to think in a
non-traditional manner.
29- We were asked to think creatively. He said that
we should read good books but also bad books as
possible comparisons. So I read everything.
This is true even for my scientific career. -
- A typical topic for our essay in our Chinese
writing the philosophy of a pig. -
- So we start to dream about anything interesting.
-
- I was not the best in my high school. I did not
have the highest grade in mathematics. But I
think deeper than my classmates and I read much
more books.
30- I entered The Chinese University of Hong Kong in
1966. I chose mathematics as my career although
I was also very interested in the subject of
history. - By this time, I started to digest those advanced
level mathematics books that I read in high
school. I did not quite understand those books
at the beginning. Suddenly I understand them and
I was much better than the contemporary students.
31-
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-
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32Chung Chi College Anthem Men from four seas
founded Chung Chi so that here might youth Honour
Christ, eternal teacher, who Himself is
truth. Through the long night keep the torch
bright and the work begun Till the lights of
faith and knowledge show the world made
one. China's still evolving culture, grateful,
we retain East and West, through freely sharing,
further strength obtain, By the Church upheld and
nurtured, minds to duty drawn, Chung Chi, toward
the very highest, lead us on, and on!
33- College mathematics opened my eyes. The fact
that one can derive every statement in
mathematics from simple axioms really excited me.
After I understood how mathematics was built, I
got so excited that I wrote a letter to my
professor showing my great pleasure. It was a
cornerstone for my appreciation of mathematics. -
- A new Ph.D came from Berkeley to Hong Kong. His
name is Stephen Salaff. He was so impressed by
my performance that he wrote a book with me
together. Its topic is on ordinary differential
equations.
34- Another teacher Dr. Brody came from Princeton.
He had a rather unique way of teaching. He
picked an advanced book in mathematics. He
assigned a chapter for the students to find
mistakes in the book and corrected the mistakes. -
- It is a good method to train us not to depend on
textbook. At the same time, I trained myself to
be critical about the established theorems in the
book. Sometimes I generalized the theorems.
Brody was very pleased by my performance when I
showed what I could do in class.
35- The importance of such trainings is that
- I learnt how to think independently.
- I found out how important it is to express
mathematics in front of an audience. - These points have been important for me and for
my teaching.
36- With the help of Dr. Salaff, I was able to enter
the graduate school of Berkeley despite that I
did not finish my college in Hong Kong. -
- Of course, Berkeley has the leading mathematics
department in the world. I arrived in August. I
met Prof. S. S. Chern who become my thesis
advisor later.
37- When I was in Hong Kong, I was too much
fascinated by very abstract mathematics.
(Although I was trained quite solidly in
analysis.) I thought mathematics covering a very
general area is best mathematics. I thought I
would study functional analysis. I learnt a lot
in that subject. I read a big fat book of
Dunford-Schwatz on functional analysis. I also
read a lot of books on operator algebra. -
- When I arrived in Berkeley, I met some best minds
in mathematics. I changed my view.
38- When I met those first rated mathematicians, I
was rather thirsty in learning different subjects
from them. I attended many classes from 8am to
5pm. (Sometimes I ate lunch in class.) These
are subjects ranging from topology, geometry,
differential equations, Lie groups, number
theory, combinatorials, probability theory to
dynamical system. I did not understand all of
them. But I focus my efforts on several of them.
39- When I learnt topology, it was so differently
from what I learnt before. There were fifty
students in class. All of them seem to be smart
and far better than me. They could perform and
talked nicely. -
- However, I did my home work well and in a short
time, I found out that I was not bad, after all.
The key is to work out all those tough home works
and think about them thoroughly.
40- I read a book of John Milnor and was fascinated
by the description of the concept of curvature.
John Milnor is an excellent topologist. -
- I started to think about problems that is related
to questions in the book. I spent a lot of time
in the library. - There was no office for graduate students. There
were many famous professors in Berkeley. Soon I
realize that they are human beings after all. I
read many journals and books in the library.
41- I started to be able to prove some nontrivial
theorems in the second quarter. They are related
to some theorems in group theory that I learnt
over some casual conversation with a teacher in
college. I applied it to geometry. My
professors were surprised and pleased by my
progress. One of the professors started to work
with me. We wrote two papers. Professor Chern
was on sabbatical leave. When he returned, he
was very pleased.
42- I did not think what I did was great. I was very
impressed by Prof. Morrey on his teaching of
nonlinear partial differential equations. He
taught nonlinear technique. It was not
fashionable. The book he wrote was difficult to
read. I thought those technique that he
developed are very deep and must be important for
the future of geometry. I learnt those
technology. Despite of Prof. Morreys big name,
very few students or faculties cared about his
course. At the end, I was the only student in
class and Prof. Morrey taught me in his office.
This course built the foundation of my
mathematics career.
43- After I wrote several papers, Prof. Chern told
many people how brilliant I was although I did
not think he knew my works well. I started to
think more thoroughly about mathematics and
geometry in particular. I worked on other parts
of geometry. However, results did not come easy. -
- My friend S. Y. Cheng came from Hong Kong that
summer. We shared an apartment right next to the
campus and I became more relax.
44- In that summer, I asked Prof. Chern to be my
advisor. He agreed and after one month, he said
that my papers in the first year should be enough
for my thesis. I was surprised because I thought
they are not good enough and I wanted to learn
more. -
- In any case, in the second year, I learnt more in
the field of complex geometry and topology.
Prof. Chern had a great expectation on me. He
suggested me to work on Rieman hypothesis.
Unfortunately up to now, I never thought about it.
45- Instead I pursued the general understanding of
curvature of space. I decided a key to
understand such a concept was a proposal made by
Calabi in early fifties. Nobody believed what
Calabis thought is true. I started to think
about it. It is not the standard thing that a
geometer would do in those days. It is clearly a
hard question of analysis. Nobody would touch
such problem.
46- I started to develop my taste into learning how
to introduce analytic methods into geometry.
Previous to this, there were attempts to apply
nonlinear theory to surfaces in three space. I
wanted to deal with an abstract space in
arbitrary dimension. -
- Because of Prof. Morrey and Cherns interests in
minimal surfaces, I also developed interest into
this fascinating subject. In particular, I was
interesting into harmonic maps. In general, I
studied Calculus of variation.
47- I was interested in all analytic aspects of
geometry. The basic idea is to merge the subject
of nonlinear differential equation and geometry.
In order to understand nonlinear equation, it is
fundamental to understand linear equations.
Hence I establish the first major theorem for
harmonic functions on manifolds. I got my friend
S. Y. Cheng to look into eigenvalue and
eigenfunction problems. Together we wrote
several important papers on the subject. They
are still fundamental for modern research.
48- When I graduated, I got several offers. My
teacher Chern suggested me to go to Institute for
Advanced Study. The salary was less than half of
what I could have gotten from Harvard. But I
went to the Institute for Advanced Study. I met
some other group of distinguished mathematicians.
I developed some taste into topology, especially
the theory of symmetries of space. I did solve
some important problems in this subject based on
analytical ideas I developed (group actions on
manifolds).
49- Because of problem of visa, I went to New York
State University of Stony Brook. At that point,
it was supposed to be the center of metric
geometry. It was indeed a good place, full of
energetic young geometers. I learnt their
technique. But I did not think that was the
right direction for geometry. -
- After one year, I went to Stanford where there
was no geometer. It is a very peaceful
environment and is very good in nonlinear partial
differential equations. I met my very good
friend Leon Simon and my former student Richard
Schoen. Together we developed the subject of
nonlinear analysis in geometry.
50- Tao Yuan-Ming (?????)
- Long I lived checked by the bars of a cage. Now
I have turned again to Nature and Freedom. - ?????,??????
51- When I arrived at Stanford, there was a big
conference in geometry. A physicist was involved
to give a talk on general relativity. - Although I did not understand Physics well, I
immediately fell in love of the geometry problem
associated to general relativity. It is
fascinating to give physical meaning of space
that we saw and vice versa.
52- The problem was too difficult to solve at that
time. But I kept that in mind. - During the conference, I thought I found a way to
disprove the proposal of Prof. Calabi. I was
asked to give a presentation of my thoughts. It
all sounded good. Nobody objected. So every
people was happy that the general expection was
true the Calabi Conjecture is wrong after all.
53- After two months, Prof. Calabi wrote to me for
clarification of my thoughts. - I found a serious gap on my reasoning. It was
the most painful period of my research life. I
could not sleep.
54- For about two weeks, I could not sleep as I
considered that my reputation was badly damaged
by not able to reproduce what I claimed.
(Although I never wrote any announcement of it.)
However, the pain of going through of each single
details of the problem convinced me that the
opposite direction should be right. The argument
to give counterexample to the Calabi Conjecture
was that if it were true, something must happen.
Hence a few years later, when I settled this
problem, I knew many natural consequences of it.
55- After I decided that it must be true, I worked
towards the right direction. Many preparatory
works were done to prepare for the final proof.
I worked with Cheng on understanding my questions
related to Monge-Ampere equations, affine
geometry, maximal surfaces and many related
problems. Richard Schoen worked with me on
harmonic maps. Schoen, Simon and I worked on
minimal surfaces. In a matter of two years, we
understood a great deal of nonlinear analysis
related to geometry. It was an exciting period
of time in geometry.
56- Qu Yuan (??)
- This is what I am after.
- I will not turn back even nine deaths are ahead.
- ???????,????????
57- Right after I got married, I got the right idea
to finish the proof of the Calabi Conjecture. I
felt I finally understood curvature of Kahler
geometry. - Many important applications were found to solve
some old problems in algebric geometry.
58September 2, 2003
One Cosmic Question, Too Many Answers
One problem is that string theory requires 10
dimensions of space-time, whereas we appear to
live in four. Dr. Strominger remembered being
excited when he found a paper by the
mathematician Dr. Shing-Tung Yau, now of Harvard
and the Chinese University of Hong Kong. It
proved a conjecture by Dr. Eugenio Calabi, now
retired from the University of Pennsylvania, that
the extra dimensions could be curled up in
microscopically invisible ways like the loops in
a carpet.
59- When I finished the proof of the Calabi
Conjecture, I felt I have set up a framework for
mathematicians to merge two important fields
together nonlinear partial differential equation
and geometry. - In 1976, I was in UCLA and I met my friend Meeks
who was my classmate in graduate school. He was
not in good shape. But he was a very original
mathematician. So I proposed to work with him on
relating ideas from minimal surfaces and
topology of three dimensional manifold together.
60- We had a great success. We solved two classical
problems in both fields - If the boundary of a soap film is convex, the
soap film cannot cross itself. - Together with works with Thurston, the famous
problem of Smith Conjecture is solved. - Once the direction was set in the right way, many
classical questions can be answered.
61- Next year, I visited Berkeley where I gave
seminars on nonlinear problems in geometry. Both
Richard Schoen and S. Y. Cheng were there. With
Schoen, we finally solved the problem that I was
excited about in general relativity. - The problem is called positive mass conjecture
and is fundamental for general relativity. (Only
if the mass is positive that spacetime can be
stable.)
62- In 1978, I returned to Stanford, I applied ideas
of minimal surfaces to solve a famous problem
(Frenkel Conjecture) in complex geometry with
Y.T. Siu. I also introduced ideas of harmonic
map to studying discrete group symmetries. These
ideas are still useful up to now. - Schoen and I developed the structure theory of
manifolds with positive scalar curvature based on
our works on general relativity.
63- In 1979, we had a special year in differential
geometry in the Institute for Advanced Study.
Practically all geometers came. We set a good
direction for geometry. I proposed one hundred
interesting open problems for the field of
geometry. Some of them were solved and some of
them were not. - The 1970s have been one of the most fruitful era
of geometry.
64- By late seventies, I was well-recognized by my
colleagues. There were many news coverage on
problems that I solved. - However, it will be misleading to think that my
goal is to earn medals and gain recognition. It
has never been the priority of my study. - I am interested in Mathematics because it is so
exciting to see how human thought can be extended
to understand nature. The beauty of nature from
the point of view of geometry is everlasting.
65- Together with my friends Schoen, Simon, Cheng,
Meeks, Uhlenbeck, Hamilton, and later by
Donaldson, Taubes and Huisken, and others,
Nonlinear Analysis in Geometry has been
established as a rich subject. Its importance in
understanding beauty of nature can never be
underestimated. The most recent developments
show their importance in Physics and in Applied
Science.
66- Once a natural merge of several great subjects
Geometry, Non-linear Analysis, Algebraic
Geometry, Mathematical Physics, is done,
classical and difficult problems were naturally
solved. Problem solving can be considered as
lampstands on our road to understand nature.
67- Confucius (??)
- Studying without thinking goes nowhere thinking
without studying leads to bewilderment. - ??????,???????
68- Han (?? 600 AD) on the process of learning
- When general people praise my writing, I am not
pleased. - When general people slight my writing, I am not
depressed. - ???????,????????
69C.F. Gauss (1817)
- I am becoming more and more convincing that the
necessity of our geometry cannot be proved, at
least not by human reason nor for human reason.
Perhaps in another life we will be able to obtain
insight into the nature of space which is now
unattainable. - Until then we must place geometry not in the same
class with arithmetic which is purely a priori,
but with mechanics.
70Lets now demonstrate an old concept of geometry
to computer graphics
- An abstract two dimensional space with complex
coordinates is called Riemann surface. - In the following pictures, we use these concepts
to draw a map over the surfaces of a teapot, a
bunny, and a minimal surface. Note that this map
is a generalization of latitude and longitude of
the globe. They are orthogonal to each other.
71Application of Gaussian Curvature to Face
Recognition
Note that the color on the face corresponds to
level sets of the Gaussian curvature of the face
72Riemann Surface
- Holomorphic transformation between surfaces
demo
73- In the last ten years, my coauthors and I are
very much involved in understanding the role of
fundamental physics in geometry. In order to
gain the intuition behind the motivation from
physics. I spent a lot of time attending their
seminars in physics department. We were able to
obtain deep theorems in mathematics based on this
interaction. A very important concept is duality
74- Duality is a beautiful and elegant concept.
- It says that some theory with strong coupling is
the same as other theory with weak coupling. - It is very similar to Chinese Taoism or Yingyang.
- But the concept of duality is more rigorous and
quantitive. It enables us to calculate some
mathematical quantities that are otherwise
difficult to calculate.
75- I do not hesitate to say that mathematics
deserves to be cultivated for its own sake, and
that the theories of not admitting applications
to physics deserve to be studied as well as
others. - - H. POINCARE
- ??????,????,???????????????????,??????,??????????
- - ???
76- and, believe me, if I were again beginning my
studies I would follow the advice of Plato and
start with mathematics. - - GALILEO
- ?????,????,?????????,?????
- - ???
77My father took part in the establishment of the
Chinese University in its early stages. His
three sons, including the speaker, were educated
in the same school. I am deeply honored to be
able to make contribution towards the university.
78Hong Kong has played an important role in modern
history. There are many outstanding scholars
from Hong Kong who are now working all over the
world. Among the four Hong Kong professors in
Harvard, it is interesting to observe that three
of them have been professors of the Chinese
University. I firmly believe that under the
support of our government and our society with
vision, Hong Kong is the city with the greatest
potential to nourish future Nobel or Fields
laureates. Our university should see this as a
goal, not a burden.
79Alumni of Mathematics Department http//www.math.
cuhk.edu.hk/alumni
80Thank you !